Anatomy & Organs

Epithelium – structure, function & diseases


Epithilia are cells from glandular and connective tissue . The name represents a collective term, which is also known under the designation “surface-covering cell layer”. The tissue has important functions that can be influenced by various diseases.

What are epithelia?

Epithelium can consist of one or more layers of cells. There are different cell types that differentiate themselves on the basis of different characteristics. For example, multilayered epithelial cells can be found in the esophagus and vagina, while monolayered epithelia are localized in the area of ​​the gastric and intestinal mucosa .

Multi-row epithelial cells are found in the airways , transitional epithelium in different elements of the urinary system. All body surfaces are surrounded by epithelia on the inner and outer side in humans. Only the joint capsules and the bursa are exempt from this rule. In addition to muscle, nerve and connective tissue, the cells represent another type of tissue. In the epithelial tissue there is normally only a small proportion of blood vessels . It is important in the overall health of the skin .

Anatomy & Structure

The epithelial cells are separated from the connective tissue by a basement membrane, which consists of specific proteins . Adjacent epithelial cells, on the other hand, are in constant contact with each other. If you look at a single cell, you will notice that it contains only a very small proportion of intercellular substance. Epithelial cells are polarized, they can partially distinguish directions from each other.Their position is decisive for this property: either epithelial cells are localized between body and air or within the organism between connective tissue and lumen. In principle, they are responsible for always separating two areas from each other. The outer side is called apical. It tends toward the outer part, such as the skin or lumen. The basal side, on the other hand, is in contact with the tissue below the epithelial tissue. The connection is made via another membrane.

Function & Tasks

The functions and tasks of epithelial cells are very different and depend on various factors. Epithelial cells within glandular tissue exhibit differentiated operations than cells located in surfaces. In addition, the surrounding organ also determines the tasks of the tissue. Nevertheless, the range of tasks can be divided into protective, sensory, secretory and transport functions. The protective function is particularly evident on the surface of the skin: in order to avoid injuries and tears, the skin must be elastic and firm.

In addition, the epithelial cells ensure that the connective tissue does not detach from the skin, but is firmly anchored in it. At the same time, organs are sealed by the epithelial cells. Only in this way is it possible for the stomach contents to remain in the stomach and the food residue in the intestines. But also with regard to internal organs, the tissue is responsible for protecting against mechanical stimuli. In terms of sensory function, it is noticeable that the majority of cells in sensory organs can be localized within epithelial tissue. Here the epithelial cells are useful in that they can connect internal and external elements together.

Accordingly, epithelial cells help with vision, smell and taste. They are located in the human retina, on the back of the tongue and in the olfactory mucosa. In addition, they transmit mechanical stimuli such as temperature and pain perception to the brain. The epithelial cells are also able to remove foreign bodies via very fine hairs, so-called cilia. The body’s own secretion in the form of sweat or other substances takes place via glandular epithelial cells. In addition to secretions such as tears, hormones are also released here , such as thyroid hormones. Epithelial cells thus take on numerous and important tasks. If their function is restricted, various symptoms and complaints can occur. It is therefore advisable to see a doctor as soon as possible.


Various viruses and bacteria have the potential to invade and damage epithelial tissue. Viral diseases often involve an infection with the herpes virus . Herpes viruses can cause cells to swell and fluid to collect. In this, a high level of leukocytes can often be detected. Bacterial infections are often caused by streptococci and staphylococci .Inflammation can result from the invading and multiplying of bacteria. This is how erysipelas , for example, develops . The bacteria enter the epithelial tissue in different ways and cause swelling and pain due to widespread inflammation. The subsequent treatment also depends on the time of diagnosis. Even if this was successfully completed, a recurrence of the disease cannot be completely ruled out. Aside from pathogens, tumors can also affect the epithelial layer. These are benign or malignant changes in the tissue. Carcinomas , but also basal cell carcinomas can develop.

While basal cell carcinomas do not metastasize , they still have the potential to spread to surrounding tissue and cause further damage. The epithelium surrounds different organs. If there are diseases of the vessels which are supplied by the epithelial cells, then vascular epithelial diseases can appear. For example, capillary loops in the skin can damage the basement membrane and be responsible for blood penetrating the epithelial tissue. autoimmune diseasescan also cause detachment of the epithelial layers. This can cause allergies, itching, hives, or swelling. Immunological reactions may be responsible for the separation between the epithelium and the underlying tissue.

Typical & common skin diseases

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.